Powder injection molding binder, powder injection molding composition and method for production of sintered member

Abstract

An injection molding binder permitting formation of a molded article incapable of sustaining such defects as a crack or an expansion at the degreasing step and allowing the degreasing treatment to be completed quickly, an injection molding composition, and a method for the production of a sintered member are disclosed. The powder injection molding binder contains a polymer (I) which is obtained by polymerizing a monomer component composed of 50 to 100% by weight of a long side chain-containing monomer and 0 to 50% by weight of other polymerizable monomer. The powder injection molding composition comprises the binder, a binder auxiliary, and a powdery material capable of sintering. The method for the production of a sintered member comprises the steps of injection molding the composition, subjecting the molded mass to a degreasing treatment, and sintering the degreased molded mass.

What is claimed is: 
     
       1. A powder injection molding composition comprising (a) from 20 to 80% by volume of a powdery material capable of sintering, (b) from 10 to 70% by volume of an organic solvent soluble polymer (I) obtained by polymerizing a monomer component comprising from 50 to 100% by weight of at least one long side chain-containing monomer selected from the group consisting of (i) long side chain-containing vinyl monomers represented by the formula (1)   CH.sub.2 ═C(R.sup.1)--B--R.sup.2                       ( 1)     wherein     R 1  is H or CH 3 , R 2  is an aliphatic hydrocarbon group having from 15-30 carbon atoms and   B is --C(O)--O--, --C(O)NH.CH 2 .CH 2 .O.C(O)--, --C(O)NH.CH(OH).CH 2 .O.C(O)--, or --C(O)NH.CH 2 .CH 2 .O.C(O)NH.R 3 .NH.C(O)O-- wherein R 3  is a divalent organic group or --O.C(O)--, and     (ii) long side chain-containing maleic monomers represented by the formula (2) ##STR9## wherein R 4  is H or an aliphatic hydrocarbon group having from 15-30 carbon atoms and R 5  is an aliphatic hydrocarbon group having from 15-30 carbon atoms, and from 50 to 0% by weight of other polymerizable monomer, and (c) from 10 to 70% by volume of a binder auxiliary (II), providing the total of the powdery material, the polymer (I), and the binder auxiliary (II) accounts for 100% by volume, wherein after said composition is subjected to injection molding, said polymer (I) and said binder auxiliary (II) are removable from said injection molded product, whereby the residual molded product comprising said powdery material is sinterable to provide the desired sintered powdery material, free of said polymer (I) and said binder auxiliary (II).   
     
     
       2. The powder injection molding according to claim 1, wherein said powdery material capable of sintering is the powder of at least one member selected from the group consisting of metals, ceramic substances, and cermets. 
     
     
       3. The powder injection molding according to claim 1, wherein an average particle diameter of said powdery material capable of sintering is in the range of from 0.1 to 20 μm. 
     
     
       4. The powder injection molding according to claim 1, wherein said binder auxiliary (II) is at least one member selected from the group consisting of a binding agent, a plasticizer, and a slip additive. 
     
     
       5. The powder injection molding composition according to claim 1, wherein the amount of said polymer (I) is in the range of from 10 to 50% by volume and the amount of said binder auxiliary (II) is in the range of from 10 to 50% by volume providing the total of said polymer (I) and said binder auxiliary (II) and said powdery material accounts for 100% by volume. 
     
     
       6. The powder injection molding composition according to claim 1, wherein R 1  is H, R 2  is an aliphatic hydrocarbon group from 15 to 30 carbon atoms, and B is ##STR10## in the formula (1) and R 4  is H or an aliphatic hydrocarbon group of from 15 to 30 carbon atoms and R 5  is an aliphatic hydrocarbon group of from 1 5 to 30 carbon atoms in the formula (2).   
     
     
       7. The powder injection molding composition according to claim 1, wherein said long side chain-containing monomer is a long side chain-containing vinyl monomer represented by the formula (1). 
     
     
       8. The powder injection molding composition according to claim 7, wherein R 1  is H, R 2  is an aliphatic hydrocarbon group of from 15 to 30 carbon atoms, and B is ##STR11## in the formula (1). 
     
     
       9. The powder injection molding composition according to claim 1, wherein the polymer (I) obtained by polymerizing a monomer component comprises 80 to 100% by weight of said long side chain-containing monomer and 20 to 0% by weight of said other polymerizable monomer. 
     
     
       10. The powder injection molding composition according to claim 1, wherein said powdery material is metals.